change how walk works

engine/debug.go

@@ -2,6 +2,7 @@ package engine
 
 import (
 	"encoding/gob"
+	"errors"
 	"fmt"
 	"math"
 	"os"
@@ -12,6 +13,7 @@ import (
 )
 
 func init() {
+	gob.Register(GobDumper{})
 	gob.Register(PerfDisplay{})
 }
 
@@ -30,19 +32,32 @@ func (PerfDisplay) Z() float64 {
 // GobDumper waits for a given key combo, then dumps the game into a gob file
 // in the current directory.
 type GobDumper struct {
-	combo []ebiten.Key
+	KeyCombo []ebiten.Key
-	game  ebiten.Game
+
+	game *Game
 }
 
-func (d GobDumper) Update() error {
+func (d *GobDumper) Scan(g *Game) []interface{} {
-	for _, key := range d.combo {
+	d.game = g
+	return nil
+}
+
+func (d *GobDumper) Update() error {
+	for _, key := range d.KeyCombo {
 		if !ebiten.IsKeyPressed(key) {
 			return nil
 		}
 	}
+	if d.game == nil {
+		return errors.New("nil d.game in GobDumper.Update")
+	}
 	f, err := os.Create(time.Now().Format("20060102030405.gob"))
 	if err != nil {
 		return err
 	}
-	return gob.NewEncoder(f).Encode(d.game)
+	defer f.Close()
+	if err := gob.NewEncoder(f).Encode(d.game); err != nil {
+		return err
+	}
+	return f.Close()
 }

engine/game.go

@@ -29,7 +29,6 @@ type Game struct {
 	ScreenHeight int
 	Scene        *Scene
 
-	allComponents  []interface{}
 	componentsByID map[string]interface{}
 }
 
@@ -51,11 +50,21 @@ func (g *Game) Update() error {
 // Component returns the component with a given ID.
 func (g *Game) Component(id string) interface{} { return g.componentsByID[id] }
 
-// Walk calls visit with every component, for as long as visit returns true.
+// Walk calls v with every component, for as long as visit returns true.
-func (g *Game) Walk(visit func(interface{}) bool) {
+func (g *Game) Walk(v func(interface{}) bool) {
-	for _, c := range g.allComponents {
+	g.walk(g.Scene, v)
-		if !visit(c) {
+}
-			return
+
+func (g *Game) walk(c interface{}, v func(interface{}) bool) {
+	if !v(c) {
+		return
+	}
+	if sc, ok := c.(Scanner); ok {
+		for _, c := range sc.Scan(g) {
+			if !v(c) {
+				return
+			}
+			g.walk(c, v)
 		}
 	}
 }
@@ -63,16 +72,11 @@ func (g *Game) Walk(visit func(interface{}) bool) {
 // Build builds the component database.
 func (g *Game) Build() {
 	byID := make(map[string]interface{})
-	all := []interface{}{g.Scene}
+	g.walk(g.Scene, func(c interface{}) bool {
-	for offset := 0; offset < len(all); offset++ {
+		if id, ok := c.(IDer); ok {
-		head := all[offset]
+			byID[id.ID()] = c
-		if id, ok := head.(IDer); ok {
-			byID[id.ID()] = head
 		}
-		if sc, ok := head.(Scanner); ok {
+		return true
-			all = append(all, sc.Scan(g))
+	})
-		}
-	}
-	g.allComponents = all
 	g.componentsByID = byID
 }

main.go

@@ -75,6 +75,12 @@ func main() {
 		ScreenWidth:  screenWidth,
 		Scene: &engine.Scene{
 			Components: []interface{}{
+				&engine.GobDumper{
+					KeyCombo: []ebiten.Key{
+						ebiten.KeyControl,
+						ebiten.KeyD,
+					},
+				},
 				&engine.Tilemap{
 					Map:      tiles,
 					Src:      engine.ImageRef{Path: "assets/boxes.png"},
@@ -84,6 +90,7 @@ func main() {
 			},
 		},
 	}
+	game.Build()
 
 	if err := ebiten.RunGame(game); err != nil {
 		log.Fatalf("Game error: %v", err)